Bacon slicing machines of the type commonly used in meat packing operations have a rotatable cutting blade mounted on a motor driven shaft, and slabs of bacon supported on a bed are pushed by a ram in a direction parallel with the shaft into the cutting blade. As the blade rotates, slices fall onto a conveyor which carry them to stations where they are weighed and packaged.
Bacon slabs are notoriously irregular in shape and vary substantially in thickness. They also are irregular in that the fat and lean portions vary in density and are not uniformly distributed throughout the mass of the slab. Because of such irregularities the slicing machines in common use are not capable of forming the sliced bacon into drafts of uniform weight such as 1/2 lb., 1 lb., or 2 lb., packages which may be desired for packaging and marketing. Moreover, such machines are not capable of making a desired number of slices for each package.
Attempts have been made to regulate the thickness of the slices in accordance with the thickness of the slab. One type of machine operating on this principle employs fingers which sense the thickness of the bacon slab as the slab is advanced toward the cutting blade. U.S. Pat. No. 3,762,257 shows such a machine in which a link mechanism is sensitive to the position of the fingers and operates to control the thickness of the slices. In another type of slicing machine shown in the U.S. Pat. No. 2,954,811, radiant energy is directed through the slab so that some energy is absorbed in the meat while some passes through the meat body. The amounts of radiation which respectively pass through the meat and through a standard absorbent on the other side of the radiation source, are converted to electric currents and the difference between the amplitudes of these two currents is utilized through amplifying means to operate liquid pumps, the pumped liquid being passed into a hydraulic cylinder the piston of which is moved to drive the meat or other material to be sliced toward the slicing blade.
Attempts as above described have not been successful in commercial practice. One difficulty may be attributed to the high rate of speed at which the slicers normally run. It is common to operate the slicers at speeds which produce 500 to 1,000 slices per minute and this is a factor which puts greater demands on machines when a high degree of accuracy is required.
In machines such as disclosed in U.S. Pat. No. 3,762,257 where fingers and mechanical linkages are relied upon, it is difficult if not impossible to have the movements take place with the speed and precision required, and the necessary precision is not obtained in machines such as in U.S. Pat. No. 2,965,811 where the force which advances the meat to be sliced is the result of operating fluid pumps feeding a cylinder the piston of which moves linearly with the meat. Also, prior attempts to stop the slicing operation when the predetermined weight of each package had been reached resulted in the making of a few very thin slices which were unwanted and have been called "slivers". Perhaps this difficulty may have been attributable to some extent to the high speed of operation of the machine, but the high speeds are necessary in commercial operations.